Bioorganically-augmented high value fertilizer

ABSTRACT

The invention is directed to processes for treating biosolids that result in high-value, nitrogen-containing, slow-release, organically-augmented inorganic fertilizer that are competitive with less valuable or more costly conventional commercially manufactured fertilizers. The process involves conditioning traditional waste-water biosolids and processing the conditioned biosolids continuously in a high throughput manufacturing facility. The exothermic design and closed loop control of the primary reaction vessel decreases significantly the amount of power necessary to run a manufacturing facility. The process utilizes green technologies to facilitate decreased waste and enhanced air quality standards over traditional processing plants. The fertilizer produced from recovered biosolid waste is safe and meets or exceeds the United States Environment Protection Agency (USEPA) Class A and Exceptional Quality standards and is not subject to restrictions or regulations.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/291,205, filed Dec. 30, 2009, entitled “Bioorganically-AugmentedHigh Value Fertilizer,” which is hereby specifically and entirelyincorporated by reference.

BACKGROUND

1. Field of the Invention

This invention is directed to systems, devices, and methods for acontinuous flow manufacturing process for a fertilizer, especially ahigh nitrogen, organically augmented, inorganic, ammonium based,slow-release or controlled-release fertilizer. The invention is alsodirected to advantageously taking advantage of the exothermic reactionof mixed compounds to enhance the nitrogen composition of the fertilizerand the breakdown of unwanted macromolecules. The invention furtherdecreases the amount of greenhouse gas emissions and is basically carbonneutral. The invention is also directed to products produced by theprocesses of the invention.

2. Description of the Background

The disposal of biosolids discharged from municipal wastewater treatmentplants is a serious and growing problem. In 1990, the United StatesEnvironmental Protection Agency indicated that a family of fourdischarged 300 to 400 gallons of wastewater per day and in 2000 thisnumber has almost doubled. From this wastewater, publicly ownedtreatment works generate approximately 7.7 million dry metric tons ofsludge (or “biosolids” as these municipal sludges are now called)annually or about 64 dry pounds of biosolids for every individual in theUnited States.

The definitions of “sewage sludge” and “sludge” and “biosolids” underTitle 40 of the Code of Federal Regulations, Part 257.2, herebyincorporated by reference, is as follows:

-   -   “Sewage sludge means solid, semi-solid, or liquid residue        generated during the treatment of domestic sewage in a treatment        works. Sewage sludge includes, but is not limited to, domestic        septage; scum or solid removed in primary, secondary or advanced        wastewater treatment processes; and a material derived from        sewage sludge. Sewage sludge does not include ash generated        during the firing of sewage sludge in a sewage sludge        incinerator or grit and screenings generated during preliminary        treatment of domestic sewage in a treatment works. Sludge means        solid, semi-solid or liquid waste generated from municipal,        commercial, or industrial wastewater treatment plant, water        supply treatment plant, or air pollution control facility or any        other such waste having similar characteristics and effect.”

The term sludge also encompasses substances such as, but not limited tomunicipal dewatered biosolids, domestic septage, heat-dried biosolids,pharmaceutical fermentation wastes, microbial digests of organicproducts such as food stuffs, food byproducts, animal manures, digestedanimal manures, organic sludges comprised primarily of microorganisms,and any combinations thereof.

There are several types of biosolids produced from sewage and/orwastewater treatment. These include primary biosolids, waste-activatedbiosolids, pasteurized biosolids, heat-treated biosolids, andaerobically or anaerobically digested biosolids, and combinationsthereof. These biosolids may be from municipal and/or industrialsources. Thus, biosolids can comprise macromolecules including proteins,nucleic acids, fats, carbohydrates and lipids. Biosolids can comprisepharmaceutical compounds including waste products from theirmanufacture, antibiotics, hormones, hormone-like molecules, otherbiologically active compounds and macromolecules.

Commonly, but inadequately, biosolids are merely dewatered to the bestextent possible by chemical and mechanical means. The water content ofsewage biosolids is still very high, and none of the undesirablecompounds listed above are neutralized. Typical biosolids coming out ofa gravity clarifier may have a dry solids content of two percent orless. After anaerobic digestion, the solids content can be about tenpercent. Cationic water-soluble polymers have been found useful forcausing further separation between the solids and the water that ischemically and physically bound. Filtration or centrifugation ofcationic polymer treated biosolids typically yields a paste-likebiosolids cake containing a range of solids.

Drying of sewage biosolids (to greater than 90 percent solids) has beenpracticed for many years in both the United States and Europe. Biosolidsdrying in the United States prior to about 1965 was undertaken to reducetransportation costs and in pursuit of various disposal options. In someplants, the biosolids are dried in powder form and the fine particlesare consumed in the combustion chamber of an incinerator or boiler. Inthe late 1960's two municipalities, Houston and Milwaukee began tomarket a pelletized or granulated dried biosolids for use as a soilamendment and/or fertilizer. Several more plants for manufacture ofdried pelletized biosolids were built in the 1980's and 1990's;especially after ocean dumping of biosolids by coastal cities waseliminated. Drying and conversion to a heat-dried biosolids pelletfertilizer was the best option for these metropolitan areas wherelandfills and land for disposal were limited. However, the investmentrequired for a biosolids drying facility is very large resulting intremendous municipal costs per dry ton of biosolids.

A common biosolid that is dried and pelletized is anaerobically-digestedmunicipal sewage. Anaerobic digestion, as the name indicates, involvestreatment by facultative bacteria under anaerobic conditions todecompose the organic matter in the biosolids. After a prescribed timeand temperature, a biosolid, relatively free of putrifiable organicmatter, is obtained. Typically, pathogens remain in such biosolids, andthe USEPA has classed such treated biosolids as “Class B” implying thatthey are of a lower standard than the “Class A” treated bio solids.Because Class B biosolids contain pathogen indicators—and thereforepotential pathogens, they are restricted in the manner by which they canbe applied to animal and human crops. In contrast, Class A biosolids,e.g., heat-dried biosolids pellets, as well as the product of thepresent invention, are not restricted under current USEPA standards asfertilizer for animal or human crop usage.

If pathogens (e.g. Salmonella sp. bacteria, fecal coliform indicatorbacteria, enteric viruses, and viable helminth ova) are below detectablelevels, the biosolids meet the Class A designation. The Part 503 rule(Title 40 of the Code of Federal Regulations, Part 503, incorporatedherein by reference) lists six alternatives for treating biosolids sothey can be classified in Class A with respect to pathogens. Alternative1 requires biosolids to be subjected to one of four time-temperatureregimes. Alternative 2 requires that biosolids processing meets pH,temperature and air-drying requirements. Alternative 3 requires thatwhen biosolids are treated in other processes, it must be demonstratedthat the process can reduce enteric viruses and viable helminthes ova,and operating conditions used in the demonstration after pathogenreduction demonstration is completed must be maintained. Alternative 4requires that when treated in unknown processes, biosolids be tested forpathogens at the time the biosolids are used or disposed or, in certainsituations, prepared for use or disposal. Alternative 5 requires thatbiosolids be treated in one of the Processes to Further ReducePathogens. Alternative 6 requires that biosolids be treated in a processequivalent to one of the Processes to Further Reduce Pathogens, asdetermined by the permitting authority.

Class A pathogen biosolids must also possess a density of fecal coliformof less than 1,000 most probable numbers (MPN) per gram total solids(dry-weight basis) or a density of Salmonella sp. bacteria of less than3 MPN per 4 grams of total solids (dry-weight basis). Either of thesetwo requirements must be met at one of the following times: when thebiosolids are used or disposed; when the biosolids are prepared for saleor give-away in a bag or other container for land application; or whenthe biosolids or derived materials are prepared to meet the requirementsfor Exceptional Quality biosolids.

All biosolids applied to the land must meet the ceiling concentrationfor pollutants, comprising ten heavy metal pollutants: arsenic, cadmium,chromium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc.If a limit for any one of these is exceeded, the biosolids cannot beapplied to the land without the incorporation of significantrestrictions. Exceptional Quality (EQ) is a term used by the USEPA Guideto Part 503 Rule 7 to characterize biosolids that meet low-pollutant andClass A pathogen reduction (virtual absence of pathogens) limits andthat have a reduced level of degradable compounds that attract vectors.

Pathogen reduction takes place before or at the same time as vectorattraction reduction, except when the pH adjustment, percent solidsvector attraction, injection, or incorporation options are met. Finally,vector attraction reduction must be met when biosolids are applied toland. Commonly, this is achieved by drying the biosolids product to alevel of greater than 90 percent solids.

Biosolids that are merely dried, as with heat-dried pellets, even ifdried to greater than 90 percent solids, have several disadvantages foragricultural use. Biosolids have a low fertilization value, typicallyhaving nitrogen content of only about two to five percent. Freight andapplication costs per unit of nitrogen are high. The heat-driedbiosolids often have a disagreeable odor, particularly when moist. Also,dried pellets have low density and hardness and when blended with othercommercial fertilizer materials, the pellets may segregate, anddisintegrate and may not spread on the field uniformly with other moredense ingredients. The disagreeable odor associated with the use ofbiosolids, unless adequately treated, will continue to be present duringfurther processing of a nitrogen rich fertilizer product, and cancontinue to be present in the final product. This complicates theplacement of suitable fertilizer processing plants to locations that arenot in close proximity to residential communities. Additionally, thelonger distance that biosolids must be transported adds to the cost andlogistics of disposing of this waste product. Another disadvantage tocurrent biosolids-enhanced fertilizers is that bacterial action maycontinue when the material becomes moist, and under storage conditions,the material's temperature may rise to the point of auto-ignition.Hence, except for special markets that value its organic content forsoil amendment or filler in blended fertilizer, there is relatively poordemand for the heat-dried biosolids product. In many casesmunicipalities must pay freight charges, or may offer other incentivesfor commercial growers to use the material. However, this is frequentlystill more economical than alternative disposal schemes.

The market value for agricultural fertilizers is principally based ontheir nitrogen content. A need exists for a practical, safe and economicmethod for increasing the nitrogen content of biosolids to a levelapproaching that of commercial mineral fertilizers, e.g., eight totwenty percent. If such a biosolids fertilizer could be manufacturedthen the overall value of the biosolids product and demand for theproduct would likely increase. Moreover, a properly manufacturedbiosolids fertilizer will have an advantage in that much of its nitrogenwill be of the slow release type. Slow-release or controlled releasefertilizer is one in which the nutrient, e.g., nitrogen, becomesavailable in the soil column at rates much slower than fast-availablenitrogen as from traditional fertilizers such as urea, ammonium sulfateand diammonium phosphate. This is very desirable and provides nitrogento the plant throughout the plant growing cycle with the implicationthat less nitrogen needs to be applied to the soil or crop therebyreducing the potential of environmental contamination and reducing thecost of fertilizer usage. Traditional inorganic manufactured slowrelease nitrogen fertilizers have a price many times that of ordinarymineral nitrogen fertilizers. Under the scenario of high nitrogenbiosolids-containing fertilizer production from their biosolids,municipalities would enjoy public and regulatory support for theirbiosolids disposition program. Such a program would ensure the regularremoval of their dewatered or dried biosolids, for example, by recyclingbiosolids into a high nitrogen fertilizer which then can be solddirectly into the mature national fertilizer distribution industry,thereby eliminating one of the major problems traditionally associatedwith biosolids treatment programs.

Prior attempts have been made to reach some of these objectives. U.S.Pat. Nos. 3,942,970, 3,655,395, 3,939,280, 4,304,588, and 4,519,831describe processes for converting sewage biosolids to fertilizer. Ineach of these processes a urea/formaldehyde condensation product isformed in situ with the biosolids. Thus, the processes require thehandling of formaldehyde, a highly toxic lachrymator and suspectedcancer-causing agent.

Other processes require costly process equipment and/or specialconditions not readily incorporated in existing sewage treatmentfacilities (see, Japanese Patent No. 58032638; French Patent No.2,757,504).

A simple method for increasing the nitrogen in biosolids would be toblend commercial nitrogen fertilizer materials to the wet biosolidsprior to drying and pelletizing. There are only a few high-nitrogenfertilizer materials that are economical for use in agriculture.Examples include: ammonia (82 wt. percent N), urea (46 wt. percent N),and ammonium nitrate (33.54 wt. percent N). Ammonia has high volatilityand is subject to strict regulation of discharges to the atmosphere.Urea is a solid that adsorbs moisture quite readily and makes the sludgemore difficult to dry. Urea is also highly susceptible to breakdown toammonia by the microbes and enzymes in biosolids if they are notproperly prepared, resulting in nitrogen loss and an odor problem.Ammonium nitrate is a strong oxidizer and can result in a potentialexplosion problem which has all but eliminated this fertilizer from thecommercial market after 2000. All of these fertilizers have highnitrogen content, but are less than ideal for combining with biosolidsabsent special processing.

Other references, such as European Patent No. 0143392, Japanese PatentNo. 9110570 A2, and “Granulation of Compost From Sewage Sludge. V.Reduction of Ammonia Emission From Drying Process”, Hokkaidoritsu KogyoShikenjo Hokoku, 287, 85-89 (1988)) fail to disclose the use of acidswith ammonium sulfate additions and do not discuss the issue ofcorrosion of steel process equipment under acid conditions.

Over the past thirty years alkaline stabilization of biosolids has beena standard and successful method of making biosolids into beneficiallyuseful materials that can be used principally as soil-conditioningmaterials. Because these alkaline stabilized biosolids products havehigh calcium carbonate equivalencies, they have been produced andmarketed as Agricultural liming or Ag-lime materials, usually as areplacement for calcium carbonate in farm soil management strategies.Because of this usage, the value of these materials has been restrictedto only a few dollars per ton of product. However, transportation costsare high in large part due to the significant water content of thematerial. Amounts of water up to fifty percent render transportationeconomically and geographically restricted to areas close to the sourceof their treatment.

Thus, there is a long standing need for practical means of increasingthe economic value of sewage biosolids through increasing its nitrogencontent, and increasing the ability to be spread as well as a need totreat these materials such that they are converted into commodityfertilizers with physical and chemical and nutrient properties such thatthey can command significant value in the national and internationalcommodity fertilizer marketplace. A series of U.S. Pat. Nos. 5,984,992;6,159,263; 6,758,879 and 7,128,880 describe methods of production ofhigh nitrogen organically enhanced ammonium sulfate fertilizers madewith biosolids utilizing a pipe-cross reactor as originated by theTennessee Valley Authority. The pipe, tee and pipe-cross reactor aredefined by the IFDC in the Fertilizer Manual (1998), p 440 as: “the pipereactor consists basically of a length of corrosion-resistant pipe(about 5-15 m long) to which phosphoric acid, ammonia and often waterare simultaneously added to one end through a piping configurationresembling a tee, thus the name ‘tee reactor.’ The tee reactor wasmodified by TVA to also accept an additional flow of sulfuric acidthrough another pipe inlet located opposite the phosphoric acid inlet,giving the unit a “cross” configuration and thus the name “pipe-crossreactor”.

Both the IFDC Fertilizer Manual (1998) and the Fertilizer Technical DataBook (2000) refer to the pipe-cross reactors. Pipe-cross reactorsdeliver a concentrated mix to the granulator shaping device and moreefficiently evaporate undesired water from the fertilizer mix than otherdevices, but these references demonstrate a long-felt need forimprovement, indicating that one of the shortcomings of the pipe-crossreactor is scale formation inside the pipe which can result in clogging.

The methodologies taught by this group of patents (U.S. Pat. Nos.5,984,992; 6,159,263; 6,758,879 and 7,128,880) are plagued by problemsrelated to the blockage of these narrow relative to their lengthreaction “pipe-like” reactor configurations during operation and relatedto the difficulty of control of the reaction temperature and pressureand retention time of the mix within such pipe-cross reactors. Thesepipe-cross reactors are narrow in contrast to their length, e.g., up tosix to eight inches in diameter and often fifteen feet in length orlonger. The plant practicing the manufacture of organically-enhancedammonium sulfate fertilizers often had to shut down and disassemble thepipe-cross reactor either due to blockage from biosolids buildup or fromdestructive over heating in such reactors such that the commonly usedTeflon® coating on the interior-reaction side of the reactor was meltedand ruined. Further, the use of the pipe-cross reactor has the distinctdisadvantage of having very short reactor retention times (usually lessthan twenty seconds) which is an advantage in the manufacture oftraditional fertilizers like ammonium sulfate but is a disadvantage whencoupled to the simultaneous process of biosolids. Such short processingtime increases the probability of untreated or non-homogenous mixing asthe three material inputs pass through this reactor. Also limiting isthe lack of control over the atmospheric pressure within such pipe-crossreactors since these reactors have open-ended discharges usuallydirectly into a granulator. Related to but distinct from the lack ofcontrol of internal pressures, pipe-cross reactors also have little tono temperature control over the mix passing through the reactor.

U.S. Pat. No. 4,743,287 to Robinson describes a method to use tworeaction vessels in sequence to incorporate organic biosolids intonitrogen fertilizers of low or medium nitrogen concentration (a range offour weight-percent nitrogen to a maximum of nitrogen concentration often weight-percent). Robinson uses his first reaction vessel to achievevery low pH values of the mixture (pH 0.2 to 1.5) to achieve hydrolysisof molecules present and to prepare the mix for reaction in a secondreaction vessel. Robinson does indicate that a single reactor can beused, but only in a batch configuration and not in a continuous flowmanufacturing method. Robinson also indicates that the acid and ammoniamay not be injected in any order, but must be injected in sequence. Thispatent describes the reaction vessels capable of achieving highpressures (30 psig) with relatively long retention times as compared tothe pipe-cross reactors. However, Robinson fails to meet the need for anovel and practical continuous flow method of manufacturing highnitrogen (greater than 8 wt. percent nitrogen) and biosolids-containingfertilizer products under the advantages of defined temperatures,pressures and reaction retention times. Thus, an urgent need exists foran effective, efficient, and economical process for treating biosolids.

SUMMARY

The present invention overcomes the problems and disadvantagesassociated with current strategies and designs and provides new toolsand methods for the processing of biosolids into a safe commerciallyviable natural slow-release fertilizer.

One embodiment of the invention is directed to methods for a continuoustreatment of biosolids comprising: forming an acidified paste ofdewatered biosolids and one or more first acids; adding the acidifiedpaste to a pressure vessel such that the pressure vessel maintains ahead space wherein the head space has a predetermined pressure; addingone or more second acids and one or more bases to the pressure vessel tocombine with the acidified paste and form a mixture; subjecting themixture to a temperature and pressure for a retention time, wherein thetemperature and moisture content of the mixture are determined by thehead space pressure; removing the mixture from the pressure vessel; anddrying the mixture to form treated and dried biosolids. Biosolids thatcan be utilized comprise one or more of municipal biosolids, heat-driedbiosolids, pharmaceutical fermentation wastes, microbial digests oforganic products, food stuffs, food byproducts, animal manures, digestedanimal manures, organic biosolids, biosolids containing microorganisms,or combinations thereof. Dewatered biosolids are preferably created bysubjecting biosolids to filtration, centrifugation, pressure, or acombination thereof. Preferably, the one or more first acids comprise atleast phosphoric acid at a concentration of 50% or more, and morepreferably 54%. Preferably, the acidified paste has a pH of from pH2-6,and more preferably from pH 3-4. Also preferably, the one or more secondacids comprise phosphoric acid, sulfuric acid, or both, and the one ormore bases comprise anhydrous or aqueous ammonia. More preferably theone or more second acids comprise sulfuric or both sulfuric andphosphoric and the pH is less than pH 2 and more preferably less thanpH 1. Preferably the one or more bases is anhydrous ammonia and the pHincreases to pH 2.5-4 or higher. The one or more second acids and theone or more bases together with the acidified paste create an exothermicreaction within the mixture. The pressure applied to the mixtureprevents boiling and quiets the overall reaction allowing thetemperature to have maximal effect on the macromolecules within thebiosolids. Preferably the exothermic reaction takes place withoutexternal heating and the mixture is maintained at a temperature of 230°F. or greater. Optionally, one or more ferrates and/or one or moreoxidizing agents may be added to the mixture. Preferably, the one ormore ferrates are a calcium ferrate, a sodium ferrate, a potassiumferrate, ferrous sulfate heptahydrate, or combinations thereof. Alsopreferably, the one or more ferrates are formed from reaction of asolid-state sodium hydroxide with sodium hypochlorite and ferricchloride. The one or more oxidizing agents are preferably hydrogenperoxide, calcium hypochlorite, sodium hypochlorite, potassiumhypochlorite, chlorine dioxide, ozone, oxygen, or combinations thereof.Retention time of the mixture within the pressure vessel is preferably30 minutes or less, more preferably 15 minutes or less, and even morepreferably 10 minutes or less. One or more of acidity, pressure, flowspeed, pH, and base infusion speed are preferably controlled byclosed-loop computer controls to maintain a predetermined reactiontemperature. Also preferably, the biosolids are continuously processedthrough the pressure vessel, thereby continuously forming the treatedand dried biosolids. Macromolecules within the treated and driedbiosolids are partially or preferably completely hydrolyzed, denatured,and/or sterilized. Organic material within the biosolids may include oneor more of pharmaceutical compounds, antibiotics, hormones, hormone-likemolecules, biologically active compounds, macromolecules, carbohydrates,nucleic acids, fats, lipids, proteins, or combinations thereof.Preferably the phosphate content of the dried mixture is from 0.5% to4%, and the nitrogen content is enhanced by aqueous ammonia that isadded to the reaction vessel. Preferably, a granulating agent is addedto the mixture before drying to form a dried and granulated mixture. Themethod may also involve crushing the dried and granulated mixture andpassing the dried and granulated mixture through one or more screens toisolate granules of a predetermined size. The dried granules may also becoated with a coating agent that is applied to the granules within acooling apparatus that cools the dried and granulated mixture to atemperature of 140° F. or less. A preferred cooling apparatus is afluidized bed, an ammonia chiller, or a rotating drum.

Another embodiment of the invention is directed to methods as describedabove and involving passing the reaction mixture through a secondpressure vessel.

Another embodiment of the invention is directed to methods furthercomprising adding one or more plant nutrients to the mixture in thepressure vessel. Preferred plant nutrients include urea, ammoniumnitrate, ammonium sulfate, monoammonium phosphate, diammonium phosphate,urea ammonium nitrate, liquid urea, potash, iron oxide, soluble iron,chelated iron and combinations thereof. One or more hardening agents mayalso be added to the mixture. Preferred hardening agents include ferricoxides, alum attapulgite clay, industrial molasses, lignon, lignosulfonate, urea formaldehyde polymerize and combinations thereof.

Another embodiment of the invention comprises methods for treatment ofbiosolids comprising: combining dewatered biosolids with an acid to forma mixture; injecting the mixture and steam into a pressure vesselcontaining a pressurized head space; subjecting the mixture to apredetermined temperature and pressure for a retention time, wherein thetemperature and moisture content of the mixture are determined by thehead space pressure; removing the mixture from the pressure vessel afterthe retention time; and drying the mixture.

Another embodiment of the invention is directed to biosolids treated andprocessed by the methods of the invention.

Another embodiment of the invention is directed to systems forprocessing biosolids into fertilizer, comprising: a first mixer thatblends the biosolids with concentrated acid and oxidizing agents andconverts the biosolids into a pumpable paste; a pressure vessel with ahead space pressure that receives the pumpable paste from the firstmixer, wherein the pressure vessel retains the pumpable paste at apredetermined pressure and temperature as determined by the head spacepressure and for a period of time; a second mixer that receives thepumpable paste from the pressure vessel, wherein the pumpable paste ismixed with a hardening agent; and a granulator to break the hardenedpaste into pelletized fertilizer. Preferably, the system contains asteam generator, wherein steam produced by the steam generator isinjected into the first mixer. Also preferably, the system comprises aplurality of valves to control at least one of steam levels, mixturelevels, temperature, presser, pH, and nitrogen levels, wherein airdischarge from the facility is less than 30 CFM. The system may furthercomprise an ammonia vaporizer and a baghouse dryer.

Another embodiment of the invention is directed to pressure vessels forprocessing biosolids according to the methods of the inventioncomprising a head space and a plurality of valves that control headspace pressure, wherein head space pressure determines the temperatureand moisture content of biosolids within the vessel, and furthercomprising gauges that indicate one or more of temperature, pressure,pH, and nitrogen content of the biosolids within the pressure vessel.

Other embodiments and advantages of the invention are set forth in partin the description, which follows, and in part, may be obvious from thisdescription, or may be learned from the practice of the invention.

DESCRIPTION OF THE FIGURES

FIG. 1. Biosolid Fertilizer Plant Flow Chart.

FIG. 2. Pressure Vessel Reaction Hydrolyzer.

FIG. 3. Detail of Ammonia and Sulfuric Acid Injection into Hydrolyzer.

FIG. 4. Biosolid Fertilizer Plant Air Flow Diagram.

DESCRIPTION OF THE INVENTION

Biosolids, especially in the form of sewage sludge from wastewaterprocessing, pose a major disposal problem and community expense.Traditional processing results in dewatered biosolids that poses an odorand potential pathogen problem. Alternatively, processing can produce afine powder that is either burned or transported to disposal sites.Biosolids processing may also involve heat treatment to inactivatemicroorganisms and other potentially contaminating materials. Theseprocessed biosolids are considered low-value fertilizers and dispersedon crops and large agricultural areas. All of these solutions areunsatisfactory and attempts have been made to sterilize the biosolidsfor use as a fertilizer with minimal success.

It has been surprisingly discovered that high-value fertilizer can beefficiently manufactured from raw and semi-processed biosolids. Theefficiency involves a continuous flow manufacturing process augmentedwith nitrogen from ammonium and possibly other nitrogen sources as well.The invention also takes advantage of the thixotropic property thatresults from the preliminary processing of biosolids. Vigorousagitation, mixing or other shear action of the preliminary processingproduces a pumpable fluid. The invention preferably involves creating anexothermic reaction that breaks down and destroys macromolecules. Theprocess preferably involves controlling unwanted odors through theaddition of odor-control agents and odor control processing steps. Themanufacturing facility for the process of the invention minimizes theamount of water needed, as well as the overall power utilization andamount of waste byproducts formed. Thus, manufacturing can be sized toservice the needs of the size of the particular community in which theplant is located. This tailoring design allows for a biosolidsprocessing/fertilizer manufacturing plant that can process less than 3tons per hour of dewatered biosolids or scaled up for larger plants(e.g., up to 10 to 12 tons per hour or more). This sizing featurereduces costs, allows for standardization with interchangeable equipmentand the efficiency of the operational logistics as well as overallliability. Manufacturing plants of the invention preferably allow foradjacent storage facilities. Being adjacent, transportation logisticsare simplified or eliminated thereby reducing transportation costs ofthe product as well as the transportation costs of input biosolids. Theinvention preferably provides for an odor control system to ensurecommunity acceptance of the manufacturing plant and to facilitatemeeting USEPA standards as well as making the process more efficientthrough the capture and incorporation of valuable nitrogen or otherpotential and/or fugitive plant nutrients from the processed air of theplant.

One embodiment of the invention is directed to processing biosolids asclose to the treatment plant as possible, minimizing transport andpotential spillage of potentially harmful compounds. This isaccomplished by taking biosolids directly from waste water treatmentplants. Preferably the biosolids are dewatered to 18 to 30 percent solidcontent. Taking advantage of the thixotropic property of many types ofdewatered biosolids to take on the properties of pastes or paste-like,pump-able fluids, the biosolids are pumped into a pug-mill. Thispumpable biosolid is preferably initially conditioned by injection ofsteam, water, and heat from inline heaters to further enhance the flowof the biosolids for further conditioning in a double shafted pug-mill.In this initial pug-mill the biosolids are thoroughly mixed or blendedwith chemical additives such as oxidizing agents, for the initial odorcontrol and to prepare the biosolids for reaction in the pressurevessel. In this step the initial acidification and odor control of thebiosolids are also achieved by infusion of a black or agricultural gradphosphoric acid at a strength of 50 percent or greater and preferably 54percent strength. This phosphoric acid is added such that the finalconcentration of phosphate in the fertilizer granules is between 0.5percent and 6 percent and preferably between 1.5 percent and 4 percentand more preferably between 2 percent and 3 percent. Additionally, oneor more plant nutrients can be added to this pug-mill to enhance thecomposition of the biosolids paste to prepare it as a fertilizer.Ferrous sulfate heptahydrate also can be added to facilitate additionalpurification of the bio solids paste.

After the biosolids exit the first pug-mill, they are pumped to thepressure vessel where liquid ammonia and sulfuric acid is injected intothe biosolids, resulting in an exothermic reaction and preferably aviolent one. The pressure vessel is constructed in a manner to allow avigorous continuous exothermic reaction with the conditioned acidicbiosolids paste and ammonia. In another embodiment of this invention,the residence time through the pressure vessel is up to 15 minutes attemperatures exceeding 230° F. (110 C). In a preferred embodiment, theentire reaction process is controlled by a closed loop computer controlthat continuously monitors and adjusts the exothermic reaction throughaddition of sulfuric acid, ammonia, plant nutrients, pH adjusters andpressure control. The preferred control mechanism is through adjustmentof the head space pressure above the biosolids in this pressure vessel.In the preferred embodiment this head pressure is controlled between 35and 80 psig (or higher), more preferably 62 psig, which regulates thelevel of the mix within the pressure vessel and thereby controls theoutflow of the mix exiting the vessel. Other embodiments of thispressure level have been conducted at pressures as low as 20 psig and ashigh as 60 psig. The entire process is carried out without the need foradditional application of heat or stopping the continuous flow ofbiosolids into and out of the pressure vessel. The biosolids, due to thetemperature, pressure, mixing and retention time in the hydrolysisvessel undergo partial or complete hydrolysis, denaturization,sterilization, or combinations thereof for the components of theconditioned biosolids.

Upon exiting the upper portion (preferably allowing for a 25 percenthead space volume above the biosolids) of the pressure vessel theconditioned reactive mixture of biosolids enter a second pug-millwherein the final adjustments are made to the biosolids in preparationfor drying. The pH at this point is preferably from about 5.5 to about7, and more preferably 6.2. Odor control agents can be addedcontinuously from the initial flow into the first pug-mill, through thepressure vessel, and in the final pug-mill processing.

After processing through the second pug-mill further drying,granulation, screening, packaging and recycling of processed biosolidsoccur. In a preferred embodiment upon exit from the second pug-mill thebiosolids enter a granulator, which forms the pellets/granules of thefinished high nitrogen fertilizer. They are then processed through arotary dryer, which further dries the bio solids fertilizer to less than1% water content. Upon exiting the rotary dryer the biosolids fertilizeris further screened for size and separated into product, undersize andoversize granule groups. The undersized particles are recycled back intothe entrance of the second pug-mill. The oversized particles are sent toa hammer mill where they are crushed and then recycled back into theentrance of the second pug-mill. After leaving the screening process thebio solids fertilizer granules are processed through the rotary coolerwhere the biosolids fertilizer is cooled. The fertilizer granules emptyinto the final polishing screens to remove undersize granules or dustcreated in the cooling process. After processing through the polishingscreens, the product passes through a coating drum where a coating agentthat inhibits dusting is added. The biosolids fertilizer is thenwarehoused ready for bulk shipping or subsequent packaging. Anotherembodiment of the invention is the air polishing system thatcontinuously recycles the hot air generated in the cooling process tothe drying stage resulting in a reduction in fuel usage and waste airfor processing. The air drawn from the screens and equipment is cleanedin a dust collector, cooled through a heat exchanger and reused as inletair to the cooler. The heated air discharging from the cooler is againcleaned in a dust collector. The cleaned, heated air is used as inletair for the rotary dryer.

In another preferred embodiment the liquid ammonia infusion lines arepassed through a heat exchanger placed in the dryer discharge airstream. Ammonia is vaporized and superheated in the heat exchanger andis then utilized in the reactor which increases energy to the criticalchemical reaction zone of the process and significantly reduces the fuelenergy required for drying. In an additional benefit of this heatexchange, the dryer discharge air stream is partially cooled by theammonia vaporization reducing the cooling load on the discharge airtreatment system.

An output of the biosolids processing of the invention is a highnitrogen, slow release biosolids fertilizer. In a preferred embodimentthe invention results in a 16-2-0-17-1-15(Sodium-Phosphorus-Potassium-Sulfur-Iron-Organics) slow release granularfertilizer that is 99 percent dry and exceeds the United StatesEnvironmental Protection Agency (USEPA) Class A requirements andExceptional Quality (EQ) Standards. The 16 percent controlled-releaseorganic nitrogen component helps bind the nitrogen in the root zone whenand where it is needed.

The invention comprises a major improvement as compared to traditionalor conventional fertilizer manufacturing practices in which a largemanufacturing facility is located as far away from communities aspossible thereby requiring that input materials be shipped over longdistances to operate the plant. A good example of this problem was thebiosolids conversion-to-fertilizer plant located in Helena, Ark. whichpracticed the manufacturing processes taught in U.S. Pat. Nos.5,984,992; 6,159,263; 6,758,879; and 7,128,880. For this fertilizermanufacturing plant, the biosolids containing between 70 percent and 80percent water were shipped to the facility from areas of New Yorkincluding New York City and Westchester County. This transportationrequirement adds a tremendous cost to the manufacturing process. Thepresent invention eliminates this type of problem by locating thephysical equipment necessary to perform the manufacturing processadjacent or close to the source of the biosolids. Such sources aretypically municipal wastewater treatment plants. For example, theprocesses of the invention have the advantage that they may beinterfaced with other unrelated ammonium production facilities. Thosefacilities may be associated with an unrelated commercial enterprisesuch as, for example, nylon or steel production. In these two industrieshot ammonium sulfate is created as a by-product to the manufacture ofproduct. By co-locating a processing facility of the invention at thesetypes of sites, the otherwise unwanted by-products such as ammoniumsulfate need not be carted away, but can be directly utilized in themanufacture of fertilizer according to the present invention.

The present invention allows for the treatment of most any organicbiosolids materials, such as municipal dewatered biosolids, domesticseptage, pharmaceutical fermentation wastes, and microbial digests ofother organic products such as food stuffs and/or animal manures ordigested animal manures, to name a few. These biosolids are typicallyfrom 12 to 40 percent solids and preferably between 18 and 30 percentsolids. This treatment process can preferably result in the productionof a granular or pelleted USEPA Class A fertilizer product of suitabledryness, hardness, and chemical quality to produce a valuable,high-nitrogen, slow release commercial fertilizer product that iscapable of competing in the national and international marketplaceagainst traditional inorganic fertilizers. A commercial, high-nitrogenfertilizer preferably has greater than 8 percent nitrogen by dry weightof the finished fertilizer and more preferably at least 16 percentnitrogen by dry weight of the finished fertilizer. The Class Acharacteristic refers to the microbiological quality of the finishedfertilizer product, which meets the United States EnvironmentalProtection Agency Class A microbiological standards for a productcontaining municipal bio solids as defined in 40 C.F.R. §503. Theprocesses of the present invention meet or exceed this standard on thebasis of the stress condition and the retention time utilized, and onthe basis that the finished fertilizer is greater than 80 percent, andmore preferably greater than 90 percent dry solids with the optimallevel being over 98 percent dry solids in composition. Thus, ensuringthat the associated USEPA Vector Attraction Standards are met (90percent or greater), that the finished fertilizer granule is optimizedfor minimal water content increasing hardness characteristic andeliminating water with respect to transportation of the finishedfertilizer. Hardness is provided by adding to the fertilizer mix, priorto shaping, one or more hardening agents selected from the groupconsisting of ferric oxides, alum, attapulgite clay, industrialmolasses, lignon, lingo-sulfonate, urea formaldehyde polymerization andcombinations thereof.

The processes of the present invention produce a fertilizer that ispreferably safe to handle and work with and preferably meets and/orexceeds the minimum requirements of a USEPA Class A biosolids.Fertilizer product is preferably sterilized and biological and chemicalcontaminants are at least partially and preferably completely hydrolyzedand denatured to the point of inactivation and/or destruction. Typicalbiological or chemical contaminants include, but are not limited to oneor more of pharmaceutical compounds, antibiotics, hormones, hormone-likemolecules, biologically active compounds, macromolecules, carbohydrates,lipids, proteins, nucleic acids, and combinations thereof.

The present invention preferably includes a stress conditioning over apredetermined retention period that creates an autoclave effect. Thisautoclave effect destroys and/or inactivates or simply sterilizes thebiosolids. Microorganisms in the biosolids, including for example,bacteria, viruses, fungi, parasites, parasite eggs, bacterial and fungalspores and combinations thereof, re destroyed and/or inactivated. Inaddition, the processes of the invention are preferably designed tohydrolyze macromolecules such as proteins, nucleic acids, lipids, fats,carbohydrates and combinations thereof, and/or other biologically-activesubstances that may be present.

According to preferred aspects of the invention, biosolids are subjectedto stress conditions, which include, but are not limited to one or moreof extremes of pH, agitation, elevated pressures, and elevatedtemperatures, which, combined with a controlled or predeterminedretention period, result in a mix and/or a fertilizer that is safer ascompared to product processed utilizing conventional technologies suchas pipe-cross reactor technologies. The capability to control orpredetermine the retention period is important in selecting thepreferred properties of the resulting product. In other words, retentiontime (R) of the biosolids in the pressure vessel is preferablydetermined on the head pressure (p) and the volume (v) of material inthe reactor (i.e., R∝p·v). Head pressure also determines the temperaturewithin the pressure vessel. Some preferred pressures and the resultingtemperatures are shown in Table 1.

TABLE 1 Pressure (psi) Temperature ° F. (C.) 20 258.8 (126)   30 274(134.4) 38 284 (140)   60 307 (152.8)

According to the preferred processes of the invention, a pressurecontrol system maintains the desired pressure in the vessel at the headpressure, which in turn sets the desired temperature and simultaneouslycontrols the level of material in the pressure vessel at thepredetermined elevation. Preferred pressures include those listed aboveand higher, including 70 psi, 80 psi and higher. More preferably thehead space pressure is about 62 psi. The pressure system preferablynegates any pluggage due to the combination of the pressure andreactions occurring with the pressure vessel itself caused by mixingunder the particular stress conditions selected. Control of the pressurealso facilitates control of the ideal moisture for the reaction vesselas well as the ultimate moisture required for proper granulation andminimal drying energy. The pressure system preferably controls thedesired pressure only at the level of the overflow. The system does notchange the level of material with the vessel unless the system fails.Thus, when biosolids are subjected to controlled stress conditions ofthe reaction vessel (e.g., heat, pH, pressure) the biosolids as well ascontaminants that are present are preferably completely inactivated. Byadjusting the stress conditions, as can be determined empirically bythose skilled in the art, a desired level of treatment can be achieved.Retention times can be set for most any period of time from minutes tohours and preferably are for a period of less than 60 minutes, morepreferably less than 30 minutes, more preferably less than 15 minutes.Preferred retention periods are from 2 to 16 minutes or 1 to 12 minutes,and more preferably about 10 minutes or less. A series of mixers ispreferably employed that may optionally be heated (e.g., single shaftedor double shafted pug-mill type mixers, preferably a blending and mixingpug-mill utilizing an adjustable broad-shaped blade configuration).Additionally, the primary pressure reactor preferably incorporatesmixing apparatus to insure sufficient agitation and mixing of biosolidswith acids and injection of reactive ammonia species along the reactionpath. The reaction between the concentrated acid or acids and theammonia is violently exothermic and creates high heat, which maintainsthe resultant ammonium salt in the soluble molten state and any waterpresent in the form of superheated steam. This exothermic reaction alsocreates significant pressure within the pressure vessel. This ammoniumsalt mix has a temperature characteristic that is about 100 C (212° F.)or higher and preferably a temperature of 121 C (250° F.) or higher, andmore preferably a temperature of 149 C (300° F.) or higher, all of whichmay be dependent upon the nature of the ammonia being used in thereaction. If anhydrous ammonia is used, the temperature is preferablysignificantly higher than when aqueous ammonia is used, especially at 21percent nitrogen.

The temperature and fluidity of the ammonium melt or salt is maintainedsuch that when blended with the biosolids in the receiving pressurevessel, the temperature of the blend will meet of exceed 100 C (212° F.)and preferably meet or exceed 149 C (300° F.). The higher temperaturesfacilitate the hydrolysis of proteins and peptides in the biosolids inan acid environment creating advantageous properties to the finalfertilizer product that result in increased crop production compared tofertilizers that do not contain such organic material (e.g., ammoniumsulfate or ammonium phosphate or urea fertilizers). The pressure vesselpreferably contains pressure and temperature gauges along its length formonitoring the pressure and temperature and further injection ports foradding additional reactive agents. The reactor vessel preferablypossesses control systems that function as a closed loop systemcontrolling the temperature, pressure, pH, reactive injection additions,and rate of flow of the molten fertilizer melt through the system.

Biosolids treated according to the processes of the invention typicallycontain low levels of metals such as arsenic, cadmium, copper, lead,mercury, molybdenum, nickel, selenium and/or zinc. Low levels are levelsbelow what are considered harmful and less than the Exceptional Quality(“EQ”) standard for metals as published by the USEPA for productscontaining municipal biosolids.

By exceeding the USEPA regulation and the hydrolyzing conditions of thehydrolyser or pressure vessel for macromolecules (e.g., personalpharmaceutical products such as antibiotics or hormones or hormone-likesubstances), the resulting fertilizer is safe for use in and aroundfarming, plants, and animals. Further, biosolids treated according tothe processes of the invention are safe for handling by and aroundhumans.

FIG. 1 provides a schematic diagram of an embodiment of the presentinvention, wherein the process of this embodiment utilizes dewateredmunicipal biosolids combined with additional plant nutrients, ammoniumsalt fertilizers, and binding agents. In this embodiment, the biosolidsto be treated is a dewatered biosolids, often referred to as a“biosolids cake.” This biosolids are delivered to the manufacturingfacility where they are stored in a storage bin 105 until the biosolidsare ready to be conditioned. The conditioning initially takes place in afirst pug-mill 110 by a vigorous mixing or blending with concentratedacid for odor control and acidification, along with oxidizing agentssuch as ferrate, which converts the thixotropic biosolids into apumpable mix, paste, or paste-like mix. The oxidizing agent reacts withreduced sulfur compounds and other odorants present in the biosolids.The concentrated acid slightly acidifies the biosolids and, if the acidis phosphoric acid, assists in modifying odorants present in thebiosolids. The exothermic reaction of this acidic mixture attainstemperatures exceeding 230° F. (110 C), which obviates the need forapplied heating. Preferably, steam from a steam generator 115 can beinjected at the beginning of the pug-mill 110 to facilitate startup andflow of the biosolids into the plant and also to enhance the exothermicreaction. As the biosolid melt proceeds through the sealed pug-mill 110additional plant nutrients can be infused into the mix. Once the mixexits the pug-mill 110 it is pumped into a pressure vessel 120 where theprimary nitrogen infusion reaction occurs. As shown in FIGS. 2 and 3, asparger 210 injects ammonia gas or other nitrogen source into the meltalong with the infusion of sulfuric acid to induce a highly exothermicreaction in the acidified biosolids that infuse the biosolids paste.This reaction is carefully controlled to optimize temperature, pressure,retention time, pH, and nitrogen, all of which can be empiricallydetermined based on the input biosolid materials and the desired outputcontent of treated and dried biosolids. The pressure vessel 120 includesa plurality of valves 215 that allow the addition of steam from steamgenerator 115, other additives, and can be used to control thetemperature, presser, and pH and nitrogen levels. The nitrogen source125 that is pumped into the pressure vessel 120 comprises a base, suchas anhydrous or aqueous ammonia. A mix of biosolids and ammonium sulfateand ammonium phosphate is formed that becomes molecularly integrated inthat the ammonium ions become electrically bound to the amphotericorganic molecules from the bio solids thereby creating a slow-release orcontrolled release nitrogen in the final fertilizer granule. Similarly,this electric bonding can occur between the sulfate and phosphate andiron molecules present in the mix thereby rendering these nutrientmolecules similarly to a slow-release or controlled release state. Thismix is maintained in a stress condition for a retention period asdetermined by its retention time (which in turn is based on the headpressure and volume as described herein) as the mix moves through thepressure vessel 120. The stress condition preferably includes elevatedtemperature, and/or elevated pressure. The elevated temperature isproduced partly or entirely by the exothermic reaction of thecomponents, which can increase the temperature of the mix to 230° F.(110 C) or greater. At these temperatures steam is generated from themix. This steam is allowed to exit the pressure vessel 120 undervalve-controlled release, accomplishing a partial drying of the mix. Thestress condition the biosolids undergo in the pressure vessel 120 andthe retention period are controlled so as to result in the production ofa mix that is sterile and that contains hydrolyzed macromolecules fromthe biosolids. Control of the stress condition and the retention periodalso results in the fusion of the ammonium ions formed with the organicmolecules present creating a natural slow-release property for thenitrogen present, and the denaturization and or hydrolysis of manymacromolecules present in the biosolids, such as proteins. When suchmolecules are biologically active, this denaturization and/or hydrolysisrenders them less active or inactive thereby creating a safer mix forpublic usage or exposure. The retention time to induce the necessaryfertilizer properties and biological inactivation are controlled by thecontinuous pumping and flow of the biosolids into the pressure vessel120. This continuous flow processing of the invention versus thetraditional batch processing of older plants aids the high throughput ofthis invention. The continuous flow also minimizes the problemsassociated with clogging of the process necessitating down time to clearthe clog. When the biosolids mix flows from the pressure vessel 120, itexits into a second mixer or pug-mill 130, where the biosolid is mixedwith a hardening agent or agents, as well as with additional nutrientsto fine tune the fertilizer. If a melt was formed in the pressure vessel120 from partial ammoniation with excess acid, the mix is also spargedwith an additional amount of a nitrogen source comprising a base, suchas ammonia, preferably vaporized ammonia in order to complete theammoniation thereby forming ammonium salt. Preferably, liquid ammonia isadded and converted to vaporized ammonia prior to entering the spargersin both the pug-mill 130 that follows the pressure vessel 120 and thegranulator 135. This conversion to vaporized ammonia improves operationof the plant as well as reduces energy requirements. The liquidanhydrous ammonia is converted to superheated ammonia vapor by means ofa heater in order to complete the ammoniation process started in thepressure vessel 120. The heating may be by a direct heater applied tothe ammonia delivery line or may be by a heat exchanger installed torecover excess heat from elsewhere in the process. As shown in FIG. 4,the excess heat may be, for example, in the dryer discharge air streamdownstream of the baghouses and prior to the acid scrubbers. The ammoniaside of the vaporizer is controlled at 90 to 120 psig, and preferably at100 psig (ammonia saturated at 64° F. {17.8}). The ammonia vapor issuperheated with the temperature controlled at 120-200° F. (48.9-93.3 C)and preferably at 170-180° F. (76.7-82.2 C). Replacing liquid ammoniawith vaporized ammonia in the recycle pug-mill 130/granulator 135ammonia spargers provides several benefits, e.g. completing theammoniation process started in the pressure vessel; improving reactionefficiency by increasing surface area of ammonia to contact unreactedacid; increasing energy efficiency by using waste heat from the processto increase the temperature of the granulator stream thereby increasingevaporation in the granulator 135 and reducing dryer energy required;reducing dust creation and increases granule size and hardness byproviding even distribution of ammonia to the reaction zone in thepug-mill 130/granulator 135 (droplets of liquid ammonia can create dustwhen small localized areas of high pH are created in the uncuredgranules, and vapor ammonia eliminates this problem); reducing therequired water quench by cooling the dryer discharge gas stream andutilizing the heat; or combinations thereof.

Next, the mix is preferably further treated by granulation or extrusioninto granules such as pellets or other, smaller structures. The granulesare dried in rotary dryer 140 and passed through one or more screens 145to separate oversized materials and undersized materials fromproper-sized materials. The oversized materials can be crushed in acrusher or mill. Subsequently, the undersized materials and the crushedoversized materials can be recycled to the second mixer or pug-mill 130to facilitate the granulation of the fertilizer mix. The resultingproper-sized granules are then dried in rotary cooler 150, sized,coated, cooled and stored. When a traditional granulator is used in theshaping process, ammoniation by vaporized ammonia and recycle additionmay occur in that vessel as well. Water removed from the mix as steamfrom the pressure vessel and from subsequent vessels as steam and/orwater vapor may be condensed and preferably returned to the wastewatertreatment plant (WWTP), or may be treated and discharged into adjacentwater resources, or into the atmosphere.

A preferred element of the invention involves treating biosolids byconditioning the biosolids by mixing with a force sufficient to renderthe biosolids pumpable. The biosolids can be further conditioned byadding one or more oxidizing agents and/or by adding one or more acidsto reduce the pH of the biosolids. The conditioning typically occurs ina mixer or a pug-mill, which can optionally be heated. The conditionedbiosolids are then added to a pressure vessel. Subsequently orsimultaneously once the process reaches steady-state, one or more acidsand one or more nitrogen sources are combined within a reaction zonelocated within the pressure vessel biosolids. The reaction zone is anarea of optimal application of any acid, any base, any nitrogen source,and any combination thereof, in order for the biosolids to be treated inembodiments of this invention. The reaction zone is optimized based onthe size of the vessel into which the biosolids are placed. The reactionzone size varies depending on the inflow of acid, base, and/or nitrogensource, as well as on the viscosity of the biosolids. The reaction zoneis preferably located in the bottom portion of the biosolids in thepressure vessel, preferably as low as possible, so that the weight ofthe materials in the vessel presses down on it, thereby helping tocontain any force generated by the exothermic reaction. The reactionzone is the portion of the biosolids into which acids, bases, and/ornitrogen sources are injected. Use of the term “reaction zone” is notintended to imply that reaction occurs only within the reaction zone.While the initial combination of the reactive components and the initialexothermic reaction occurs in the reaction zone, the exothermic reactioncontinues to occur throughout the vessel. At least one of the one ormore nitrogen sources comprises a base, and so an exothermic reactioncan take place between the acid and the base. Subsequently, this mix ismaintained in a stress condition for a retention period. The stresscondition can result in the partial hydrolysis and/or denaturation ofany macromolecules including proteins contained in the biosolidscomponent of the mix. The stress condition can also result in thepartial hydrolysis and/or denaturation of any personal pharmaceuticalcompounds, antibiotics, hormones, hormone-like molecules, or otherbiologically active compounds. The stress condition and the retentionperiod can create an autoclave effect over extended temperature andpressure exposures that destroys by sterilization any microorganismspresent in the biosolids, including bacteria, viruses, fungi, parasites,and parasite eggs. The stress condition can include agitating the mix,an increase in temperature and/or pressure due to any exothermicreaction of the components of the mix. Temperature increases of the mixdue to the stress condition preferably exceed 85 C (185° F.), morepreferably 100 C (212° F.), more preferably 121 C (250° F.), and morepreferably 126 C (260° F.). Any pressure increase of the mix due to thestress condition preferably exceeds 20 pounds per square inch (psi),more preferably exceeds 30 psi, and more preferably exceeds 38 psi andmore preferably meets or exceeds 62 psi.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising conditioning via agitation andoxidation and initial acidification of an amount of bioorganic biosolidssuch as a municipal dewatered biosolids in a pug-mill; mixingconcentrated acid with ammonia simultaneously in the presence of theconditioned biosolids to create an ammonium melt (a partially ammoniatedmix) in a pressure vessel under controlled temperature, atmosphericpressure, mix retention time and water removal as steam and/or watervapor; and further processing said hydrolyzed mix via an additionalmixer, blending in optional additional conditioners, such as an ironoxide, and at least one hardener into the fertilizer mixture to controlhardness; and sparging said additional mixer with additional vaporizedor gaseous ammonia to complete the salt formation of ammonium sulfateand/or ammonium phosphate and following that via traditional granulationprocessing to create a granular organically-augmented inorganicfertilizer in the plant. Sparging of vaporized ammonia may also becarried out in the granulator as is practiced in the manufacturing ofgranular fertilizers. When iron sulfate, i.e., ferrous sulfate, or ironoxide is added to the mix, the iron is also serving as an importantnutrient in the finished fertilizer which both enhances the value of theproduct and its performance fertilizing target crops.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising conditioning via agitation andoxidation an amount of bioorganic biosolids such as a municipaldewatered biosolids; mixing concentrated acid with ammoniasimultaneously in the presence of the conditioned biosolids to create anammonium salt (little unreacted acid remains) in a pressure vessel undercontrolled temperature, atmospheric pressure, mix retention time andwater removal as steam and/or water vapor; and further processing saidhydrolyzed mix via an additional mixer, in an additional mixer blendingin optional additional conditioners, such as an iron oxide, and at leastone hardener into the fertilizer mixture to control hardness ammoniumfertilizer art and following that by traditional granulation processingto create a granular organically augmented inorganic fertilizer in theplant.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicbiosolids to produce a pumpable paste-like mix; treating the mix withone or more oxidants and acidifying the thixotropic paste in a mixer toproduce a first conditioned mixture; obtaining a high temperatureinorganic fertilizer melt comprised of partially ammoniated mixcontaining ammonium sulfate and or ammonium phosphate with excess acid;blending the hot melt with the conditioned mixture to produce a secondmixture in a pressure vessel with a temperature over 85 C (185° F.) andpreferably over 100 C (212° F.) under controlled atmospheric pressureand mix retention time and removing water (as steam and water vapor)from said mix; further processing said second mix in an additional mixerto blend in optional additional conditioners, such as an iron oxide, andat least one hardener into the fertilizer mixture to control hardnessand sparging said additional mixer with vaporized ammonia to completethe salt formation of ammonium sulfate and or ammonium phosphate;continuing to remove water from the third mixture to produce a materialthat can be further processed with traditional granulation processing orextrusion technologies; and creating an end product fertilizer from thethird mixture. Sparging of vaporized ammonia may also be carried out inthe granulator.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicbiosolids to produce a pumpable paste-like mix; treating the mix with anoxidant and acidifying the paste in a mixer with phosphoric acid toproduce a first mixture; obtaining a high temperature inorganicfertilizer salt comprised of ammonium sulfate and or ammonium phosphate;blending the hot salt with the first mixture to produce a second mixturein a pressure vessel with a temperature over 85 C (185° F.) andpreferably over 100 C (212° F.) under controlled atmospheric pressureand mix retention time and removing water (as steam and water vapor)from said mix; blending in optional additional conditioners, such as aniron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness; continuing to remove water from the third mixture toproduce a material that can be further processed with traditionalgranulation processing or extrusion technologies; and creating an endproduct fertilizer from the third mixture.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicbiosolids to produce a pumpable paste-like mix; conditioning the mixwith one or more oxidants, preferably calcium ferrate, in a firstpug-mill or mixer to produce a first alkaline mixture; then dischargingthis conditioned mix into a second pug-mill or mixer into which anammonia source is added. In this embodiment, aqueous ammonia is used asthe base. This second mixer then discharges its alkaline ammoniated mixinto the pressure vessel. The pressure vessel will receive aconcentrated sulfuric acid to produce a high temperature inorganicfertilizer melt comprised of ammonium sulfate. In this embodimentphosphoric acid is also added to the pressure vessel, which producesammonium phosphate. The phosphoric acid is added to the pressure vesselrather than to the first pug-mill as with other embodiments because toadd the phosphoric acid early in the first pug-mill would then producean undesirable exothermic reaction in pug-mill. The exothermic reactionin the pressure vessel achieves a temperature over 100 C (212° F.) andpreferably over 137.8 C (280° F.), under controlled atmospheric pressureand mix retention time and removing water (as steam and water vapor)from said mix; discharging the fertilizer mix to an additional pug-millor mixer therein using vaporized ammonia to complete the formation ofammonium salts and blending in optional additional conditioners, such asan iron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness; continuing to remove water from the third mixture toproduce a material that can be further processed with traditionalgranulation processing or extrusion technologies; and creating an endproduct fertilizer from the third mixture.

Alternatively, this embodiment of the invention is directed to methodsof manufacturing a fertilizer comprising mixing a thixotropic organicbiosolids to produce a pumpable paste-like mix; optionally conditioningthe mix with one or more oxidants and then acidifying the paste in afirst pug-mill or mixer with phosphoric acid to produce a first mixture;then discharging this conditioned mix into a second pug-mill or mixerinto which flows concentrated acid or aqueous ammonia, but not both.This second mixer then discharges its mix into the pressure vessel. Thepressure vessel then receives either an ammonia source or a concentratedsulfuric acid depending upon whether an acid or a base was added to thesecond pug-mill, thereby obtaining a high temperature inorganicfertilizer melt comprised of primarily ammonium sulfate with a smalleramount of ammonium phosphate with a temperature over 100 C (212° F.) andpreferably over 137.8 C (280° F.), under controlled atmospheric pressureand mix retention time; removing water (as steam and water vapor) fromsaid mix; discharging the fertilizer mix to an additional pug-mill ormixer therein completing the formation of ammonium salts using vaporizedammonia and blending in optional additional conditioners, such as aniron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness; continuing to remove water from the third mixture toproduce a material that can be further processed with traditionalgranulation processing or extrusion technologies; and creating an endproduct fertilizer from the third mixture.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer in the manner of the above embodiments butwith the substitution of heat-dried biosolids or organic biosolids forthe dewatered biosolids cake described herein. This dried biosolidsmaterial may range in solids from 30 percent to 99.9 percent, butpreferably and more commonly range from 90 percent to 99.9 percent inorder to be classified as Class A by the USEPA as governed by theirVector Attraction rules for biosolids or biosolids-containing material.The dried biosolids or organic biosolids material, if received aspellets or granules, must be milled to a powder before the addition ofsome water and subsequently exposed to an oxidation agent andacidification during conditioning. The conditioned biosolids can then beprocessed through the remainder of the process as described in the aboveembodiments.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer in the manner of the above embodiments butwith the substitution of three pressure vessels in order to operate theprocesses in a “continuous batch” manner. The addition of chemicals,mixing, reactions, ammoniation, removal of water and granulation orextrusion would occur as described for any of the above embodiments.

An additional embodiment of the present invention accepts dewatered ordried biosolids but does not condition them in the manner described inthe above embodiments. Instead, the biosolids are simply agitated to apumpable state; optionally water may even be added if necessary. Thesepumpable bio solids are then processed as in the above embodiments. Theoxidation agents and optionally, additional phosphoric acid for pHcontrol, nutrient addition and suppression of auto oxidation may beadded in the second mixer or pug-mill that follows the pressure vesselor may be eliminated completely. The remaining processing steps are asdescribed herein.

Incoming dewatered biosolids may be of varying percent of solids,preferably ranging from 17 percent to 32 percent solids. The biosolidscan range from 33 percent solids to 100 percent solids. When they are ofa dry solids nature, they are milled to a powder and then processedfurther.

Preferably, biosolids are in the range of 12 percent to 40 percentsolids with biosolids between 18 percent and 30 percent. This deliverymay be either through conveyors or pipes from the wastewater treatmentplant (“WWTP”) or by traditional transportation using truck, train orbarge. Upon arrival at the plant, the dewatered biosolids may be passedthrough a lump breaker or screening device to remove large foreignobjects that might damage or destroy pumps or other equipment in theprocess. The biosolids placed into a surge or holding tank or silo or alive bottom bin for accumulation and storage until processed.Preferably, the delivered biosolids may be placed in a holding tank orsilo and then transferred to the first mixing apparatus forconditioning.

If the biosolids have not been screened for contaminant removal prior tosurge storage, then they are next preferably passed through a lumpbreaking apparatus or screen device to remove any metal or rock or otherlarge foreign objects to protect the pumping and blending apparatuseslater used in the process. The solids are then transferred by screwconveyor or pump to the reaction vessel. This material is thenconditioned further with an oxidizing agent which may be selected fromthe group, calcium ferrate, sodium ferrate, potassium ferrate, ozone,hydrogen peroxide, calcium hypochlorite, sodium hypochorite, potassiumhypochorite, chlorine dioxide and oxygen itself as well as with mixturesof said oxidants. In the preferred embodiment of the present invention,the selected oxidant is injected into the initial mixing apparatus forthe purpose of oxidizing reduced sulfur compounds present in thebiosolids as well as other odorants therein contained. Further, theconditioning process conducted within the initial pug-mill also includesthe introduction of a concentrated acid, preferably phosphoric acid andmore preferably with concentrated phosphoric acid of at least 50 percentstrength and preferably a black or agricultural phosphoric acid at 54percent strength creating an acidic paste within the initial mixer.Optionally, process water and blow-down water from the air scrubbingapparatus can be infused into the initial mixer, or they may be infusedinto the biosolids immediately prior to the lump breaker if necessary.Preferably the process of the invention minimizes the amount of wateradded into the manufacturing sequence in order to reduce the energyrequirements needed for dewatering.

Mixing with oxidizing agent(s) and concentrated acid, preferablyphosphoric acid begins the process of odor control and acidifies thebioorganic material to a level of between pH 2.0 and pH 6.9, preferablybetween pH 3.0 and pH 5.0. This treatment with phosphoric acid alsoprovides a level of resistance to oxidative heating that occurs uponlong term storage of finished organic-containing granules, such ascommonly occurs with heat-dried biosolids pellets. Heating and mixing inthis initial conditioning apparatus will create a pumpable paste. In oneembodiment of the present invention, this paste is preferably heated tocontrol odors and prepare the biosolids for mixing with concentratedacid and ammonia in a pressure vessel. Said conditioning heat ispreferably imparted to the biosolids by means of an exothermic chemicalreaction. Additional heat can be delivered steam infusion.

The establishment of higher than ambient temperatures in the bioorganicmaterial ensures that the heat energy contained in the ammonium salts isadvantageously used to kill or sufficiently inactivate at least allharmful pathogens (e.g. bacterial, viral, fungal and parasiticpathogens) that were contained in the bioorganic material, especiallymunicipal biosolids, especially when aqueous ammonia is used to form theammonium sulfate or ammonium phosphate as less exothermic energy isreleased when the aqueous ammonia is applied.

Pug-mills or mixers are horizontal mixing chambers having blade-shapedblending elements mounted on a powerfully driven shaft or shafts thatrotate at a variable but controlled speed which divide, mix, back-mixand re-divide the materials to be blended multiple times a second toyield a thorough, uniform blend with reliable consistency. The blenders,pug-mills and or mixers used in the processing sequence may be eachindependently heated via a heated shaft and or heated hollow screw blademechanism or heated by means of a jacketed sleeve around the apparatus.Heating can also be optionally applied to the second mixing apparatus,preferably a pug-mill especially when aqueous ammonia is used, whereinhardeners, optional pH adjustment agents as in vaporized or gaseousammonia sparging and dry recycle are added.

Conditioning guarantees a mix with the proper consistency for injectioninto the pressure vessel. In the preferred embodiment of the presentinvention, anhydrous (99 percent ammonia) and if necessary as might berequired by permit considerations, aqueous ammonia is blended withconcentrated sulfuric acid with or without concentrated phosphoric acid,in a pressure vessel. For the purposes of this invention a customreactor vessel is fabricated. This is in contrast to the development ofthe pipe-cross reactors and as described by the IFDC in the FertilizerManual by Sephri-nix in the Fertilizer Technical Data Book.Specifically, the vessel in the present invention is designed to have alarge reaction chamber and to receive the conditioned biosolids at thebase of the vessel and both sulfuric acid and ammonia directly above thebiosolids input. The acid and the ammonia react forming ammonium sulfateand ammonium phosphate thereby forming a fertilizer mix containing theinteraction of the ammonium sulfate and/or the ammonium phosphate. In apreferred embodiment, a melt will be formed by partially ammoniating theacid in this vessel. This will improve the fluidity of the fertilizermix. The melt of ammonium sulfate/phosphate is preferably at atemperature greater than 100 C (212° F.) and preferably at a temperaturegreater than 121 C (250° F.) and more preferably at a temperature ofgreater than 126 C (260° F.). In the pressure vessel the contact timeshall be for a minimum of one minute with the preferred range of 15minutes or more with a more preferred range of 10 to 20 minutes with apreferred retention time for normal operation being about 15 minutes.The pressure vessel will contain an agitation capability using rotatingpaddles or blades. Such agitation of the mix within the pressure vesselwill help ensure uniformity and controlled reaction of the mix alongwith moving the mix continuously through the closed system. Theagitation will also prevent consolidation of the mix and will facilitatedischarge of the mix into the pug-mill.

The orientation of the pressure vessel is vertical with steam beingreleased by controlled valve at the upper end of the vessel therebypermitting the atmospheric pressure within the vessel to be controlled.Further, this pressure, greater than 20 psi, and preferably greater than30 psi, and more preferably greater than 38 psi, combines with thetemperature and pH maintained within the vessel such that chemicalalterations of macromolecules occur within the vessel. Chemicalalterations due to combined heat and pressure include partialdenaturization of protein molecules and the hydrolysis of proteinmolecules and the hydrolysis of other organic compounds. Suchdenaturization or hydrolysis of organics results in the creation of asafer final product because of the loss of biological activity oftenassociated with such compounds such as personal pharmaceuticals,antibiotics, hormones and other biologically-active organic compoundsthat were present in the biosolids.

In addition, the high stresses created in the pressure vessel, e.g.,pressure and temperature of the invention sterilizes the bioorganicmaterials for a safer, less harmful fertilizer. Sterility is measured bylack of detection of viable microorganisms.

Following achievement of said times of exposure the venting of the steamand water vapor emitted from the mix and the pressure vessel can takeplace thereby partially drying the mix from the energy imparted into themix from the chemical reaction of acid and ammonia. This steam andmoisture is captured and used to enhance the current process.

Drying of the mixture continues in the mixer or pug-mill that followsthe pressure vessel and may continue in the shaping apparatus such asthe granulator, to be completed in a dryer, as in a rotary drum dryer orfluidized bed dryer. Ammoniation is completed in this mixer or pug-millthat follows the pressure vessel by injection of vaporized ammonia ormay be optionally completed by injection of vaporized or gaseous ammoniainto the granulator.

In one preferred embodiment, the process air is acid scrubbed to removeany fugitive odorants and especially vaporized or gaseous ammonia. Thecaptured ammonia, as an ammonium salt is mixed back into the reactionvessel or mixer thereby increasing the efficiency of the entire systemand maximizing the final nitrogen concentration in the finishedfertilizer. Miscellaneous residuals including dust, non-specification orreclaimed product and dried fertilizer that is too small or undersizedor oversize material that is crushed in a crushing or mill apparatus ormay include other additives, e.g., iron that a customer would prefer canbe added to the composition of the finished fertilizer are added to thepug-mill or mixer positioned downstream from the pressure vessel. Priorto the completion of the drying process, a hardener or hardeners whichhelp to agglomerate the mix and contribute to the hardness of the driedpellet or granule are added at the pug-mill. The hardener or hardenersare selected from the group comprised of attapulgite clay, lignon,industrial molasses, and alum among others or mixtures of thesehardeners.

Optionally, dependent upon the requirements of the customer, additionalplant nutrients, for example, potash or other forms of potassium, e.g.,potassium hydroxide, are preferably added at the pug-mill. The solidnutrients that may be added also comprise urea, ammonium nitrate,mono-ammonium phosphate, diammonium phosphate, and or potash. Also addedin this second pug-mill is any additional iron required. This iron maybe of different valences, but the iron compound, known as ferroussulfate heptahydrate (FeSO₄.7H₂O), is preferable in this process as itaffects biosolids odor and enhances granulation. The iron contributes animportant and valuable plant nutrient to the fertilizer mix.

Also, additional ammonia may be sparged into the pug-mill and into thegranulator to complete the formation of the ammonium salt and to controlthe pH of the mix and to facilitate the formation of the finishedgranule. The solids used to adjust the pH may also be principallyalkaline agents selected from the group comprised of calcium carbonate,sodium hydroxide, calcium oxide, cement kiln dust, lime kiln dust, ClassC fly ash, Class F fly ash, multistage burner ash, alum, alum biosolidsfrom water treatment and wood ash. These are added via screw conveyorsat specific rates for each compound. The liquid additions also includepH adjustment materials such as acids, e.g., phosphoric acid or sulfuricacid, or caustic solutions, e.g., sodium hydroxide. These are pumped atrespective rates to the injection ring to enter the pug-mill.

In addition, pH control agents in addition to the vaporized ammoniaadded during sparging, may be added to the mixer in the form of one ormore of group of alkaline materials such as calcium oxide, calciumhydroxide, potassium hydroxide, or other metal oxides or metalhydroxides, anhydrous ammonia, cement kiln dust, lime kiln dust,fluidized bed ash, Class C fly ash and Class F fly ash addition to raisethe pH of the mix. The fertilizer product of the present inventionpreferably has a pH of between 5.0 and 7.0, more preferably between pH5.5 and pH 6.5, and more preferably between pH 5.7 and pH 6.3. Theremainder of the processing for shaping as in pellet or granuleproduction includes standard fertilizer granulation technologyespecially for high volume throughput plants. The pellet or granuleproduct, especially in smaller throughput plants considered to be thoseof less than 25 tons product production per day, may involve moreinnovative technologies such as injection or extrusion followed bymilling or spherulizing the pellet or granule or involves simpledischarge from a granulator or granulating pug-mill. When a granulatoror granulating pug-mill is used, it is preferable to feed some recycle,as in dry seed material, i.e., dry fines and fines produced by thecrusher or mill or sub-specification or reclaim material of thefertilizer product, into the pug-mill and the granulator to adjust thepercent moisture present in the mix so that agglomeration or nucleationcan occur resulting in granule formation.

Other preferred embodiments comprise adjustments to the processesdisclosed herein to control pH, dryness, nutrients in the product,shape, concentrations etc. to produce a plethora of fertilizers specificfor different plants such as roses, rhododendrons, and any otherflowers, vegetables, herbs, as well as products such as cat litters.Adjustments can also be made according to the geographic area in whichthe product is to be applied, to vary, for example, nutrients that maybe inherently or otherwise missing in the location. Examples of suchvariations include the addition of calcium, potassium or phosphorus indifferent amounts. Slow release fertilizers are the preferred embodimentof this invention.

In another preferred embodiment, the partially dry material is injecteddirectly into a vertical fluidized bed dryer to produce dry granules ina single step.

Normal drying for final drying is conducted using a horizontal fluidizedbed dryer, or a rotary drum dryer. The dried pellets or granules whichare greater than 90 percent solids and preferably are greater than 95percent solids and more preferably are greater than 98 percent and evenmore preferably are greater than 99 percent solids are then sizedthrough one or more screens. The specification size may be varieddependent upon customer requirements, however, the range of suitableproduct for sale is between 0.5 mm and 3.5 mm with the commercial rangefor normal sized fertilizer is between 2 mm and 3 mm. The presentinvention also can manufacture a minimal sized product suitable for usein golf course applications which ranges from 0.5 mm to 1.3 mm. Theproper sized material is separated and then coated and then cooled in anapparatus, preferably a rotary drum, to less than 140° F. (60 C),preferably to less than 130° F. (54.4 C) and more preferably to lessthan 120° F. (48.9 C). Coating the granule or pellet optimally occurs inthe same vessel as cooling, usually a rotary drum apparatus usingambient air or cooled air as from an ammonia evaporation cooler. Coatingmay occur in a coating vessel specifically for that purpose prior toentering the cooling vessel. Coating is with a de-duster or glazingmaterial which minimizes dust generation during transport, storage andapplication. The finished granule or pellet is then conveyed to storageas finished high nitrogen containing bioorganic-augmented inorganicammonium fertilizer until shipment from the manufacturing site. Properlycoated and dried pellets or granules have a hardness of greater than 5pounds crush resistance in order to resist dusting and handing duringtransport, shipment and application. The de-duster coating or glazingmaterial often requires a higher temperature, often 180° F. (82.2 C), tomaintain a molten condition for application in the coating apparatus.

The granule storage facility or warehouse, usually incorporating bins orsilos to contain the granules, must be dry to prevent agglomeration ofthe granules leading to degradation and destruction. The finishedproduct is upon manufacture a sterile fertilizer having substantially nodetectable amount of viable microorganisms, such as E. coli orstreptococci, harmful to animals or humans. Substantially no viablemicroorganisms means that the fertilizer is non-toxic and has nodetectable amount or a detectable amount well below a threshold for safehandling and use of microorganisms originating from the biosolids.Although the fertilizer is rendered sterile during manufacturing,contamination can be expected from air-borne microorganisms or bymicroorganisms deposited by animal or other contamination during storageor use. In any case, because the fertilizer product is dry andpredominantly inorganic ammonium salts will not support microorganismmultiplication at a rate which would lead to a public health problem.

During normal operations periodic shutdown plant equipment will benecessary for inspection, repair, or replacement. This is done todifferent degrees depending on specific situations. In one embodiment,shutdowns are automatic as in an automated command sequence provided bythe plant control processor; in another embodiment, the shutdowns arecarried out manually.

If a limited shutdown of the process is necessary to a single piece ofequipment the flow of biosolids into the reactor vessel would stop andthe unit would empty as much of the contained mix material as possibleinto the pug-mill. In this situation process water is blocked fromentering the pressure vessel which continues to run and empty throughits normal discharge. After the fertilizer mix drops to below the normaldischarge point, a diverter valve on the discharge closes sealing offthe pressure vessel normal discharge. The diverter valve at the bottomof the pressure vessel then shifts, allowing the compressed air enteringthe head space of the pressure vessel to force remaining material intothe return fertilizer mix line. If further cleaning is needed, processwater is then injected into the pressure vessel followed by compressedair to purge the water. Cleanout of the pug-mill that follows thepressure vessel, the granulator, the dryer and all subsequent equipmentis performed by running them until the vessels are empty.

The fertilizer of the present invention is preferably chemicallyadjusted to fit the needs of high nitrogen fertilizer requirementscontaining significant amounts of phosphate, sulfur and iron to enhancethe targeted nitrogen (N) content of between 8 wt. percent and 18percent by weight, and preferably 16 wt. percent permitting significantcommercial valuation.

In a modification of the preferred embodiment, two other oxidativematerials may be added to the pressure vessel. Liquid hydrogen peroxideat 25 to 50 percent concentration is added by control of a pump tobetween 1 percent and 5 percent of the biosolids delivery rate into thepressure vessel. Also, calcium hypochlorite, a solid, may be deliveredby screw conveyor to a pulverizing mill and then to an additive port ata rate equal to between 1 percent and 5 percent of the volume ofbiosolids entering the pressure vessel. An additional odor controlagent, iron oxide, Fe₃O₄, also known as magnetite, a solid, ispreferably added using a screw conveyor at a rate to a mill to pulverizeand powder these additives prior to addition to the pug-mill. Use of themill assists in optimizing these solids materials for contact with theodorant molecules present in the biosolids. The iron added here not onlyserves as an additional odor control agent, but also as a plant nutrientenhancing the usefulness and value of the finished fertilizer product.

In another embodiment of the present invention, the process is basicallyas described for previous embodiments except that a complete ammoniumsalt with no excess acid remaining is formed in the pressure orhydrolysis vessel. This then removes the necessity for ammonia spargingin the mixer or pug-mill and or the granulator.

Ammonia sparging using vaporized ammonia may be carried out in the mixeror pug-mill and or in the granulator to complete the ammoniation, pHcontrol and creation of the ammonia salt fertilizer.

Another embodiment of the present invention is practiced as any of theabove embodiments except that instead of a dewatered organic biosolids,a drier biosolids, pellets, dry organic pellets or biosolids arereceived to be processed. Water may or may not be added to startingmaterials, which may have between 12-40 percent solids, or preferably18-30 percent solids. The preferred dryness of this embodiment isgreater than 90 wt. percent solids, usually received as a heat driedbiosolids pellet manufactured at a municipal wastewater treatment plant.This dried pellet or granule usually contains less than 6 wt. percentnitrogen and more commonly, less than 4 wt. percent nitrogen, andtherefore is not desirable in the commercial fertilizer distributionsystem. This embodiment teaches the conversion of such dried lownitrogen pellets or granules into a high nitrogen organically-augmentedinorganic ammonium fertilizer. The received dry pellets or granules aremilled to a powder to facilitate production of a pumpable paste-likematerial using a combination of an oxidation agent, an acid and ifnecessary, the addition of steam or water, or condensed water from latersteps in the process.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all publications, U.S. and foreign patents and patentapplications, are specifically and entirely incorporated by reference.The term comprising, where ever used, is intended to include the termsconsisting and consisting essentially of. It is intended that thespecification and examples be considered exemplary only with the truescope and spirit of the invention indicated by the following claims.

The invention claimed is:
 1. A method for a continuous treatment ofbiosolids comprising: dewatering the biosolids to form a pump-ablefluid; injecting steam into the dewatered biosolids in a first pug-mill;mixing concentrated oxidizing agents and one or more first acids intothe dewatered biosolids in the first pug-mill; feeding the mixedbiosolids into a pressure vessel; injecting one or more second acids andammonia into the pressure vessel to combine with the mixed biosolids andform conditioned biosolids; feeding the conditioned biosolids into asecond pug-mill; treating the conditioned biosolids with one or morehardening agents in the second pug-mill; and drying the hardenedbiosolids to form a fertilizer.
 2. The method of claim 1, wherein thebiosolids comprise one or more of municipal biosolids, heat-driedbiosolids, pharmaceutical fermentation wastes, microbial digests oforganic products, food stuffs, food byproducts, animal manures, digestedanimal manures, organic biosolids, biosolids containing microorganisms,or combinations thereof.
 3. The method of claim 1, the dewateredbiosolids are created by subjecting biosolids to filtration,centrifugation, pressure, or a combination thereof.
 4. The method ofclaim 1, wherein the one or more first acids comprises at leastphosphoric acid at a concentration of 50% or more.
 5. The method ofclaim 1, wherein the one or more second acids comprise phosphoric acid,sulfuric acid, or both, and the ammonia comprises anhydrous or aqueousammonia.
 6. The method of claim 1, wherein the one or more second acidsand the ammonia together create an exothermic reaction within themixture.
 7. The method of claim 6, wherein the exothermic reaction takesplace without external heating.
 8. The method of claim 1, wherein thepressure vessel is maintained at a temperature of 230° F. or greater. 9.The method of claim 1, further comprising adding one or more ferrates tothe mixture.
 10. The method of claim 9, wherein the one or more ferratesis selected from the group consisting of a calcium ferrate, a sodiumferrate, a potassium ferrate, ferrous sulfate heptahydrate, andcombinations thereof.
 11. The method of claim 9, wherein the one or moreferrates is formed from reaction of a solid-state sodium hydroxide withsodium hypochlorite and ferric chloride.
 12. The method of claim 1,wherein the one or more oxidizing agents is selected from the groupconsisting of hydrogen peroxide, calcium hypochlorite, sodiumhypochlorite, potassium hypochlorite, chlorine dioxide, ozone, oxygen,and combinations thereof.
 13. The method of claim 1, wherein thebiosolids are retained in the pressure vessel for 15 minutes or less.14. The method of claim 1, wherein one or more of acidity, pressure,flow speed, pH, base infusion speed are controlled by closed-loopcomputer controls to maintain a predetermined reaction temperature. 15.The method of claim 1, wherein biosolids are continuously processedthrough the pressure vessel.
 16. The method of claim 1, wherein organicmaterial in the treated and dried biosolids is partially or completelyhydrolyzed, denatured, or sterilized.
 17. The method of claim 16,wherein the organic material is selected from the group consisting ofone or more members selected from the group consisting of pharmaceuticalcompounds, antibiotics, hormones, hormone-like molecules, biologicallyactive compounds, macromolecules, carbohydrates, nucleic acids, fats,lipids, proteins, and combinations thereof.
 18. The method of claim 1,wherein phosphate content of the dried biosolids is from 0.5% to 4%. 19.The method of claim 1, wherein nitrogen content of the dried biosolidsis enhanced by aqueous ammonia that is added to the pressure vessel. 20.The method of claim 1, further comprising adding a granulating agent tothe mixture before drying to form a dried and granulated mixture. 21.The method of claim 20, further comprising crushing the dried andgranulated mixture.
 22. The method of claim 20, further comprisingpassing the dried and granulated mixture through one or more screens toisolate granules of a predetermined size.
 23. The method of claim 20,further comprising coating the dried granules with a coating agent. 24.The method of claim 23, wherein the coating agent is applied to thegranules within a cooling apparatus.
 25. The method of claim 20, furthercomprising cooling the dried and granulated mixture in a coolingapparatus to a temperature of 140° F. or less.
 26. The method of claim25, wherein the cooling apparatus is a fluidized bed, an ammoniachiller, or a rotating drum.
 27. The method of claim 1, furthercomprising passing the conditioned biosolids through a second pressurevessel.
 28. The method of claim 1, further comprising adding one or moreplant nutrients to the biosolids in the first pug-mill.
 29. The methodof claim 28, wherein the one or more plant nutrients are selected fromthe group consisting of urea, ammonium nitrate, ammonium sulfate,monoammonium phosphate, diammonium phosphate, urea ammonium nitrate,liquid urea, potash, iron oxide, soluble iron, chelated iron andcombinations thereof.
 30. The method of claim 1, wherein the one or morehardening agents are selected from the group consisting of ferricoxides, alum attapulgite clay, industrial molasses, lignon, lignosulfonate, urea formaldehyde polymerizer and combinations thereof.
 31. Amethod for treatment of biosolids comprising: combining dewateredbiosolids with steam and a first acid to form a mixture; injecting themixture, one or more second acids, and ammonia into a pressure vessel tocreate an exothermic reaction; subjecting the mixture to a predeterminedtemperature and pressure for a retention time; removing the mixture fromthe pressure vessel after the retention time; and drying the mixture.